Planar electronebulization sources modeled on a calligraphy pen and the production thereof

Abstract

The invention concerns an electrospray source having a structure comprising at least one flat and thin tip (3) in cantilever in relation to the rest (1) of the structure, the tip (3) being provided with a capillary slot (5) formed through the complete thickness of the tip and which ends up at the end (6) of the tip (3) to form an ejection orifice of the electrospray source, the source comprising means of supplying (4) the capillary slot (5) with liquid to be nebulised and means of applying an electrospray voltage to the liquid.The invention further concerns a method of manufacturing said electrospray source.

Description

FIELD OF THE INVENTION[0001]The present invention concerns original electrospray sources, their method of manufacture and their applications.BACKGROUND OF THE INVENTIONState of the Prior Art[0002]Electrospraying is the phenomenon that transforms a liquid into a nebulisate under the action of a high voltage (M. CLOUPEAU “Electrohydrodynamic spraying functioning modes: a critical review. Journal of Aerosol Science (1994), 25(6), 1021-1036”). To achieve this, the liquid is conveyed into a capillary and is subjected to a high direct current or alternating current voltage or to a superposition of the two (Z. HUNEITI et al., “The study of AC coupled DC fields on conducting liquid jets”, Journal of Electrostatics (1997), 40 & 41 97-102). At the capillary output, the liquid is nebulised under the action of the voltage. The surface of the meniscus formed by the liquid is stretched to form one or several Taylor cones from which are ejected charged droplets of liquid, which develop to give a g...

AI Technical Summary

Benefits of technology

The device enables robust, reproducible, and automated nebulization with improved sensitivity and precision, suitable for mass spectrometry, drop deposition, and molecular writing, reducing human error and contamination, and integrating well with microfluidic systems.

Problems solved by technology

Nevertheless, the devices of the prior art dedicated to nanoelectrospray suffer from several weaknesses (B. FENG et al., “A Simple Nanoelectrospray Arrangement With Controllable Flowrate for Mass Analysis of Submicroliter Protein Samples”, Journal of the American Society for Mass Spectrometry (2000), 11, 94-99):Firstly, these capillaries are not very robust.

Their method of manufacture is poorly controlled and provides sources of not very reproducible dimensions;The external conductive coating deteriorates rapidly;Their mode of use is not very convenient due to their needle type geometry: the liquid to be nebulised has to be introduced manually into the needle by means of a micropipette and a suitable tip of tapered shape;The loading of the solution leads to the introduction of air bubbles in the needle, which can perturb the stability of the nebulisate at a later stage, and therefore have to be dispelled;Finally, most often, the output orifice is too small to allow the passage of the liquid; as a result, the capillaries must firstly be broken with care along one wall, which further increases the uncertain character of their dimensions.

Thus, standard commercial sources are poorly adapted, firstly to a nebulisation that is controlled, reproducible and of high quality, secondly to the use of robots due to the entirely manual character of their mode of use, and, thirdly, to an integration in a fluidic microsystem, as discussed hereafter.

These drawbacks hamper certain electrospraying application fields that require at the present time a robotisation and an automation of the processes.

However, its semi-conductive properties are not always suited depending on the targeted applications.

It is not transparent, which precludes any optical detection technique (absorbance UV, fluorescence, luminescence).

The cost of the material itself renders it unsuitable for certain mass manufacturing (in particular, unique use objects).quartz, used for the development of the first Microsystems (J. S. DANEL et al., “Quartz: a material for microdevices”, Journal of Micromechanics and Microengineering (1991), 1(4), 187-98), which has become not very attractive due to its very high cost; therefore, it has been progressively abandoned despite its physical and chemical properties.glass, a material less expensive than quartz and silicon, which is widely used due to its surface properties suited to the establishment of an electroosmotic flux (K. SATO et al., “Integration of chemical and biochemical analysis systems into a glass microchip”, Analytical Sciences (2003), 19(1), 15-22).

However, the manufacturing techniques are not as well mastered as for silicon; the etching profiles are less clean cut and the aspect ratio is very mediocre (T. R. DIETRICH et al., “Manufacture technologies for microsystems utilizing photoetchable glass”, Microelectronic Engineering (1996), 30(1-4), 497-504).

Furthermore, it is a fragile and brittle material.Polymer type materials, which group together plastics and elastomers.

Their major disadvantage is their low resistance at high temperatures and their sensitivity to the solvent conditions conventionally used in chemistry and in biology, organic, acid and basic media that can lead to a degradation of the material or even its dissolution.

Moreover, the surface chemistry of these materials is not well known, which makes difficult subsequent treatment of the surfaces brought about in order to modify their properties.

The method of manufacturing said devices in silicon by means of deep etching techniques is very complex and necessitates a costly and bulky apparatus and the performance, in terms of nebulisation voltage among others, of the structures obtained are mediocre compared to those of standard commercial sources.

Moreover, their geometry does not lend itself well to integration in a fluidic microsystem.The article of L. LIN et al., entitled “Silicon processed microneedles”, IEEE Journal of Microelectromechanical Systems (1999), 8, 78-84) describes microneedles that are connected to a microfluidic network.

The method of manufacture is moreover complex.

Moreover, the method of manufacture described is based on the machining of channels by means of a knife, a technique that does not enable channels and nebulisation devices of small dimensions to be formed.Another polymer type material, polydimethylsiloxane (PDMS), has been used in the formation of tip structures intended for electrospraying according to three different microtechnological routes, a method based on the ablation of material, a method using a double layer of photolithographic resin and a resin moulding method (international patent application WO-A-02 / 55990; J. S. KIM et al., “Micromanufacture of polydimethylsiloxane electrospray ionization emitter”, Journal of Chromatography, A (2001), 924(1-2), 137-145; J.-S.

All in all, the nebulisation devices detailed above have operating conditions that are not compliant for a small scale nebulisation (dimensions too big, nebulisation voltages too high) and most usually result from very complex manufacturing methods.

In addition, the type of structure chosen for these different devices is practically indissociable from the material used for their formation.

Finally, the application of these devices is targeted for electrospraying preceding an analysis by mass spectrometry and does not lend itself to another type of application.

Nevertheless, this technique imposes the use of a heavy, bulky, costly and complex apparatus.

These two examples indeed have a microfabricated tip that replaces the conventional AFM tip, but they do not allow one to do away with the heavy and costly peripheral machinery necessary for their operation.

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